Ready-mix concrete is concrete that is chemically specified for its purpose and then mixed, either at the concrete batch plant or by a concrete mixer truck en route to a job site, where the concrete is dispensed according to the customer's requirements. At the factory or central plant, concrete ingredients (rock, sand, cement, fly ash, water, admixtures, fiber, etc.) are funneled into the mixing drum powered by the truck. These ingredients, when mixed, are highly adhesive by nature. Accordingly, before entering public roads, the portions of the truck around the area where the ingredients were received are cleaned off to prevent buildup. As the truck travels to the job site, the mixing drum typically rotates to keep the ingredients active (i.e., not hardened) and to ensure uniformity throughout the load. At the job site, the wet concrete is discharged from the mixer through an assembly that includes one or more hoppers and one or more chutes. After the concrete is unloaded, it is necessary to clean any area of the truck that came into contact with the concrete.
Accordingly, in one embodiment, the dry ingredients for concrete may be produced at a dry batch plant and then mixed into wet concrete in a concrete mixer truck while in transit to a job site. In a different embodiment, wet concrete may be produced at a central mix plant and then transported to a job site in an agitating truck, which keeps the concrete from setting while in transit. Regardless of whether the truck actually mixes dry ingredients with water into wet concrete or simply agitates pre-mixed wet concrete, similar cleaning processes may be used. For purposes of this disclosure, “mixing” concrete and similar terms are defined as including agitating pre-mixed concrete. Thus a “concrete mixer truck” may be a truck that receives dry ingredients and mixes them into wet concrete, or it may be a truck that receives wet concrete and agitates the wet concrete to prevent premature setting.
Industry-standard practice is for the operator to manually clean the truck utilizing water from the on-board water supply, which is directed through valves to hoses mounted in close proximity to the portions of the mixer that will require cleaning. Many concrete mixer trucks have two hoses. A first hose is used for cleaning a lower portion of the truck, typically from ground level, while a second hose mounted at the top of a ladder platform is used for cleaning those portions of the truck that cannot effectively be cleaned from the ground.
The ready-mix concrete industry is, in effect, more of a perishable freight logistics business than a construction business. The contents of each truck, by design, will begin to harden within a short time after being mixed. Each load must be carefully orchestrated and every minute is valuable. Additionally, this industry operates on narrow profit margins and relies on volume to realize financial gains, so truck fleet efficiency and utilization are highly valued.